This invention relates to stages for precision movement and location, such as used in precision machines including semiconductor projection lithography equipment and, more particularly, to improved apparatus for moving a stage platform in X and Y directions.
Positioners for moving a workpiece in a projection lithography apparatus are well known. When the lithography is effected by means of an electron beam, the workpiece, and its associated platform, must be maintained in a vacuum. If the platform positioner motors are also maintained in the vacuum, this presents a problem in cooling the motors. Accordingly, it would be desirable to have the motors located in "air" while the platform being moved is located in a vacuum.
To provide smooth movement of the platform, it would be desirable to be able to use air bearings for all the moving parts. Therefore, some means must be provided for isolating the air bearings from the vacuum holding the workpiece platform.
It would also be desirable to minimize the space required for the platform positioner by having the platform and the positioner lying substantially in a plane.